Magnetic switches



July 23, 1963 D. E. REED ETAL MAGNETIC SWITCHES Filed Feb. 21, 1961INVENTORS DONALD E. REED STANLEY E REED EMMETT F. DEADY EDWARD R.FAIRBANKS BY ATTORNEY 3,698,907 Patented July 23, 1963 3.098,907MAGNETIC SWITCHES Donald E. Reed, Kensington, Md., Stanley F. Reed,McLean, and Emmett F.- Deady, Arlington, Va., and Edward R. Fairbanks,Silver Spring, Md., assignors to Space Components Inc., Washington,D.C., a corporation of the District of Columbia Filed Feb. 21, 1961,Ser. No. 90,703 Claims. (Cl. 200-87) This invention is concerned withthe art of electric switches, particularly magnetic switches having asnapaction.

Whenever switch contacts in an electrical circuit carrying a substantialload are moved to make or break the circuit, there occurs a certainamount of arcing across the contacts. This burns the contacts, deformstheir original optimum surface contour, and eventually changes theoperating characteristics of the switch to an extent that it becomesinoperative. for its intended purpose. Various expedients have beendeveloped for actuating such switches in a manner to cause a substantialsnap-action to minimize this arcing. Most attempts to solve the arcingproblem, and thereby extend the useful life of these switches, haveutilized spring-loaded elements and these elements have createdsecondary problems due to their susceptibility to fatigue and thedifficulties encountered in maintaining consistent contact alignment andpressure under such conditions.

Accordingly, it is an object of this invention to provide an improvedand simplified magnetic switch having a snap-action.

Furthermore, it is an object of this invention to provide such a switchwhich has no components under substantial compression or tension,thereby eliminating most fatigue malfunctioning thereof. I

It is another object of this invention to provide an improved structuralarrangement for a switch whereby a magnetic actuator on one side of arugged hermetically sealed wall will control switch contacts within ahermetically sealed compartment on the other side of said wall.

Still another object of this invention is to provide an improvedstructural arrangement fora very small switch for all types of loadrequirements, and specifically adapted for loads in the l0 to ampererange.

A more specific object'of this invention is to provide an electricswitch incorporating a pivotable permanent magnet on one side of abarrier to control a pivotable armature on the other side of thisbarrier.

A further specific object of this invention is to provide a switch witha rugged hermetically sealed non-corrosive contact chamber withoutorganic contaminants therein to facilitate the provision of the optimumatmosphere therewithin for the reduction of arcing, and thereby maintainpredetermined operational characteristics at temperatures up to 500 F.for periods substantially longer than other prior art switch structures.v These, together with other objects and advantages which will becomesubsequently apparent, reside in the details of construction andoperation as more fully hereinafter described and claimed, referencebeing had to the accompanying drawings forming a part hereof, whereinlike numerals refer to like parts throughout, and in which:

FIG. 1 is a partially sectional perspective view of a switchincorporating the principles of this invention;

FIG. 2 is a partially sectional side elevational view thereof;

FIG. 3 is a partially sectional front elcvational view thereof;

FIG. 4 is a top plan view thereof;

FIG. 5 is a bottom plan view of the actuator assembly thereof;

FIG. 6 is an end elevational view of the actuator assembly shown in FIG.5;

FIG. 7 is a top plan view of the armature the switch shown in FIGS. 1 to3;

FIG. 8 is a fragmentary partially sectional side elevational view of thearmature assembly shown in FIG. 7; and

FIG. 9 is a fragmentary perspective view of the actuator assembly shownin FIGS. 7 and 8, with the ferrite blocks and contacts removed to moreclearly illustrate the interlocking of the actuator assembly supportelements.

Referring now in greater particularity to the drawings, and first toFIGS. 1 to 4, there will be seen a switch constructed in accordance withthe principles of this invention and designated generally by thenumeral 1. :The switch 1 includes four unitary 'subassemblies; theactuator assembly 2, the armature assembly 3, the header as sembly 4,and the shell assembly 5. The switch 1 shown is provided with threads40, annular shoulder 41, and a pairof parallel fiat surfaces 42 tofacilitate the rigid moisture-proof installation thereof into largerassemblies. However, this particular mounting adaptation forms no partof this invention and those skilled in the art can provide switchesconstructed in accordance with this invention with various othermounting means.

The shell assembly 5 comprises a generally cup-shaped body 6 formed fromeasily machinable nonmagnetic stainless steel, such as Standard TypeNumber 303, and four flux buttons 7 hermetically sealed within" fourapertures provided at the closed end of cup-shaped body 6. Theseapertures are arranged inthe form of a rectangle, as best seen in FIG.4. Buttons 7 are in the form of small cylinassembly of ders offerromagnetic stainless steel, such as Standard Type Number 416 of highpermeability. Care must be exercised in assembling the buttons 7 withbody 6 in order to insure a hermetic seal therebetween which can beindefinitely maintained at the wide temperature range for which theseswitches are intended. A convenient as sembly process is to form theapertures in body 6 slightly larger than the diameter of buttons 7 andto silver braze buttons 7 in place utilizing the controlled clearancebetween buttons 7 and their respective apertures to form a hermetic sealby the capillary action inherent in such a method as is well known inthe brazing art. It is significant to note that in order to preserve thecorrosion resistance of body 6 and buttons 7, a low melting temperaturesilver solder, such as a compound of 45% silver, 24% cadmium, 16% zinc,and 15% copper, and a low temperature brazing flux, such as thatdistributed under the trade name Handy Flux, should be used. Theabove-described solder compound is solid at 1125 F. and liquid at l F.The above-identified flux starts to liqu-ify and become active at 800 F.and is entirely liquid and active at 1100 F. In this way, the silverbrazing of buttons 7 intobody 6 may be carried out by a very shortapplication thereto of a minimum of heat, such as by RF inductionheating at 1150 F. for 20 seconds. The corrosion resistancecharacteristics of the entirely stainless steel shell assembly arethereby retained. While body 6 and buttons 7 may be formed to size priorto brazing, it has been found expedient to leave excess metal on bothsides of the body surfaces which receive buttons 7 which are over-lengthwhen assembled- Body 6 and buttons 7 are finished after brazing toprovide smooth flux free surfaces on both the upper and 'lower surfacesof buttons 7 and the surfaces of body 6 fiush therewith.

Referring further to FIGS. 1 to 4 and more specifically to FIGS. 5 and6, the finished actuator assembly 2 comprises; a permanent magnet formedof a material such as distributed under the trade name Alnico V, twomild steel pole pieces 8 formed into the configuration shown in FIGS. 5and 6 and a non ferrous protecting strip or cover 9 which surrounds thetop and both ends of magnet 10 and pole pieces 8 to protect them frominadvertent damage during handling and usage. This assembly is formed byforming oversize pole pieces 8 to have an interior angle C plus 90, asbest seen in FIG. 5, between their flat side portions 27 and theirdepending actuating portions 28; soft soldering polepieces 8 to magnet10 at a temperature below 700 F. in such a manner as to insure that nosubstantial air gap exists between pole pieces 8 and surfaces of magnet10 adjacent thereto; finishing the top and ends of this intermediateassembly to exact size; soft soldering protective cover 9 to these threefinished surfaces at a temperature below 700 F; finishing the remainingsurfaces of pole pieces 8 to provide a central transverse channel and anangle A of approximately cleaning the finished assembly; bright chromeplating the entire assembly after copper and nickel undercoats; andthereafter magnetizing the magnet in the direction to provide a N poleat one pole piece 8 and a S pole at the other pole piece 8. It should benoted, that at no time during the fabrication of the actuator assemblydoes the temperature of the magnet 10 exceed 700 F., thereby retainingthe required operational characteristics thereof.

Referring further to FIGS. 1 to 3 and more specifically to portions ofFIG. 8, the header assembly 4 comprises two conducting contact pins 13,a center conducting pin 12 and an exhaust tube 14 integrally bondedwithin a compressive-type glass insulator 16. Insulator 16 is surroundedby a ring 15 also integrally bonded thereto. Conducting pins 12 and 13are stainless steel clad upon a copper core, and exhaust tube 14and-ring 15 are stainless steel. The intermediate assembly comprisingring 15, pins 12 and 13, tube 14, and insulator 16 hermetically bondedtogether may, be procured commercially. However, to adapt this componentfor the purposes of this invention, the upper end of pin 12 is flattenedand a center bearing pin 19 of stainless steel is resistance weldedperpendicular thereto, as best shown in FIG. 8, and contact pins 13 areflattened on their upper end and silver-cadmium oxide-steel contactbuttons 17 resistance welded thereto. It will be noted that pin 19 isupset to provide a larger diameter at the end and thereby provide abearing shoulder thereon.

Referring further to FIGS. 1 to 3 and more specifically to FIGS. 7 to 9,the armature assembly comprises two ferrite blocks 18, twosilver-cadmium oxide-steel contact buttons 23, a silver-graphite bushing20, a bracket 21 of substantially rigid beryllium copper and two mirrorimage contact support leaves 22 also of substantially rigid berylliumcopper interlocked together. Leaves 22 are resistance welded together toform a contact support arm and contact buttons 23 resistance Welded toeach other through an aperture in leaves 22, thereby integrally lockingthese four elements together. The ferrite blocks 18 and bracket 21 areinterlocked with leaves 22 by the insertion of bushing 20 between theears provided at the upper ends of leaves 22 when ears 30 are within arectangular aperture 31 in bracket 21. Ferrite blocks 18 are formed froma nickel-zinc ferrite selected for its characteristics of highresistivity of 10 ohm-centimeters, Curie point above 500 F., highpermeability at low flux density, and low coercive force. Further, eachside of ferrite blocks 18 is grooved at 32 to interlock with cars 30 ofleaves 22 and the inwardly sloping retaining edges 33 of bracket 21 whenassembled therewith. It will be noted thatv bushing 20 performs thefunction of a locking pin to retain the relative positions of thecomponents of this assembly. Bushing 20 is formed of silver-graphite andhas an internal diameter approximately .00l inch larger than thediameter of bearing pin 19 of header assembly 4 and will thereforefreely pivot thereon with a substantial wip ing action when in actualuse. It will be noted that the fiat upper surfaces of ferrite blocks 18form an angle of 180 minus B." This angle is formed in practice by thenatural bowing of bracket 21, but may be formed by bending a bracket ofmore rigid material through a suitable angle or by using a flat rigidbracket and forming ferrite blocks 18 to have a top surface angled byone half of angle B.

Referring further to FIGS. 1 to 3, the final assembly of the foursubasscmblies described hereinabove will be set forth. Armature assembly3 and header assembly 4 are cleaned; armature assembly 3 is slipped uponpin 19 of header assembly 4 with one end of bushing 20 in contact withthe shoulder formed on pin 19 by upset end 25 thereof welded to centerpin 12; retaining washer 24 is placed on pin 19 in contact with theother end of bushing 20; and the protruding end of pin 19 is deformed orcrimped at 29 to maintain thedesired alignment between these twoassemblies. This results in the formation of an armature-headersubassembly.

Further, it will be noted that body 6 has an internal shoulder 26 at theend thereof remote from buttons 7, and that the distance from shoulder26 to the internal fiat surface of body 6 which includes the innersurfaces of buttons 7 must be carefully maintained.

The armature-header subassembly and shell assembly 5 are next carefullycleaned to remove any contaminants; the armature-header subassembly thenis inserted within the generally cylindrical cavity of body 6 until theupper flat surface of ring 15 mates with internal shoulder 26 of body 6;and this position is maintained while ring 15 is silver brazed to body 6by any convenient process, the RF induction heating method describedhereinabove with respect to the joining of body 6 and buttons 7 beingsatisfactory. It should be noted that no fiux or other contaminants mustbe allowed to leak into the internal portions of the contact chamberthus formed. Following this assembly operation, this major assembly isplaced in an evacuated chamber heated to approximately 400 F. for aperiod of several hours. It is to be noted that the internal contactchamber is still open to the external environment through exhaust tube14. This major assembly is then permitted to cool in a nitrogenatmosphere and is cycled several times between nitrogen at 10 p.s.i.gage and a vacuum. Individual assemblies are next pressurized to 10p.s.i. gage with a 93% nitrogen-7% helium mixture and thereafter exhausttube 14 is resistance welded closed and the excess tube removed; oralternatively crimped closed, cut, and capped with soft solder.

Following this, actuator assembly 2 is pivotally positioned upon thisassembly with pins 11 inserted through holes in body 6 and pole pieces8, care being exercised so that no air gap exists between the topsurface of buttons 7 and the actuating portions 28 of pole pieces 8immediately adjacent to buttons 7. It will be noted that while the holesin body 6 are substantially the same diameter as pins 11, the holes inpole pieces 8 are approximately .002 inch larger in diameter than pins11 to provide for the necessary pivot-a1 action therebetween. Pins 11are lightly staked in place at the end Where they are substantiallyflush with the fiat surfaces 42 of body 6. It will be noted that whileno air gap exists between pole pieces 8 and buttons 7 whenever theactuator is in either of the switch positions, there is always an airgap of approximately .003 inch between the top surface of the raisedferrite block 18 and the underside of buttons 7 substantially parallelthereto. This air gap is required in order that the contact pressurebetween contacts 23 and 17 may be maintained even though a slightdeformation thereof occurs during the operational life of the switch.

It will be noted that in the assembled switch, the four buttons 7 areoperatively divided into two pairs, each of these pairs operativelyassociated with a single ferrite following description. Wheneveractuator assembly 2 is in contact with a first pair of buttons 7, theferrite block 18 closest thereto and the entire armature assembly 3 willbe strongly biased in a first direction toward said first pair ofbuttons 7 to minimize the small parallel .air gap in this first magneticcircuit. At the same time,

the other pair of buttons 7 are physically separated from the actuatorassembly 2 by the angular configuration thereof and the other ferriteblock 18 is separated from said other pair of buttons 7 by a relativelylarge angular airgap. This second magnetic circuit having these substantial air gaps biases said other ferrite block 18 and the entirearmature assembly 3 toward said other pair of buttons 7 in a directionopposite to said first direction.

From the above, it will be seen that one of these two magnetic circuitsis always much stronger than the other whenever actuator assembly 2 ispivoted into direct contact with shell assembly 5, and therefore,armature assembly 3 will be rotated until a button 23 contacts acorresponding button 17 to complete an external circuit connectedthereto, and thereafter retained'in this contact" position with asubstantial contact pressure due to the stronger of said two magneticcircuits.

The operation of switches constructed in accordance with this inventionis simplified since there are only two moving parts, actuatorassembly 2on one side of the closed end of shell assembly and armature assembly 3on the other side thereo Alternative structures Within 'the scope ofapplicants invention include an armature assembly similar to thatdescribed hereinabove, but with the following modifications: resilientconductivematerial substituted for the rigid material for leaves 22;soft iron blocks substituted for ferrite blocks 18; and non-conductivematerial substituted for the material for bracket 21 or the iron blocksinsulated therefrom by other insulating means, such as coating thefront, rear, and bottom of these iron blocks with a ceramic material. Itwill be seen that with this modification, the parallel air gap may beeliminated and the contact pressure maintained by the resiliency of theleaves.

' Additional modifications of applicants devices include the use of aspot of soft solder between bushing 20 and leaves 22 to improve theconductive characteristics of the armature assembly.

Further, it will be understood that the fabrication processes set forthhereinabove have been selected to minimize alignment problems. However,all the elements could be formed to exact size before assembly, providedthat sufiicient care is exercised to maintain the precise alignment ofthe component parts during assembly.-

Althou-gh specific materials and fabrication processes have been setforth in describing an exemplary embodi ment of applicants invention, itis to be understood that this embodiment is given by way of illustrationand not limitation; changes and modification-s in the details of theapparatus can be made without departing from the spirit of the inventionas defined in the appended claims.

We claim:

1. In an electrical switch, the combination comprising: a supportinghousing, said housing comprising a sealed switching cavity and a rigidwall, said wall comprising a body .portion of non-magnetic material withfour apertures therein arranged in a generally quadrangularconfiguration and an insert of magnetic material sealed within each ofsaid apertures; a magnetic actuator mounted on said housing externallyof said cavity for movement between two switching positions, saidactuator comprising a permanent magnet having N and S poles, each of 6said poles having a pair of actuating portions, said actuating portionsaligned so that one actuatingportion of each of said poles is insubstantialcontact with said wall whenever said actuator is in one ofsaid switching positions, each of said actuating portions aligned withone of said inserts; an armature within said cavity sup ported by saidhousing for pivotal movement between two switching positions, saidarmature magnetically associated with said actuator so that saidarmature assumes a predetermined angular position for each of said twoswitch positions, said armature comprising two separate blocks ofmagnetic material, a non-magnetic supporting means for said blocks,andfirst contact means mounted thereon; and second contact'means with-insaid cavity supported by said housing, whereby one actuating portion ofeach of said poles of said magnet, two of said inserts, and one of saidblocks form a strong magnetic circuit to maintain contact between saidfirst and second contact means whenever said actuator is positioned inone of said switching positions.

2. 'I'hecombina-tion set forth in claim 1 wherein said blocks have thecharacteristics of high resistivity, high curie point, permeability atlow flux density, and low coercive force.

3. The combination set forth in claim 2, wherein said strong magneticcircuit comprises a small air gap between said two inserts and saidblock for every, position of said armature.

4. The combination set forth in claim 1, wherein said blocks are mildsteel.

5. The combination set forth in claim 1 wherein said strong magneticcircuit comprises a small air gap between said two inserts and saidblock for every position of said armature.

6. In an electrical switch, the combination comprising: a supportinghousing, said housing comprising a. hermetically sealed switching cavityand first and second rigid, walls, said first wall comprising a bodyportion of nonmagnetic material with four apertures therein arranged ina generally rectangular configuration and an insert of magnetic materialhermetically sealed within each of said apertures; a magnetic actuatorsupported on a first axle mounted on said housing externally of saidcavity on One side of said first wall for pivotal movement between twoswitching positions, said first axle having an axis, said actuatorcomprising a permanent magnet having N and S poles and a magnetic axisaligned parallel to said axis of said first axle, said magnet having apole piece integrally mounted on each of said N and S poles, each ofsaid pole pieces having a pair of depending actuating portions, saidactuating portions aligned so that one actuating portion of each of saidpole pieces is in substantial contact with said one side of said firstwall whenever said actuator is in one of said switching positions, eachof said actuating portions aligned with one of said inserts; an armaturewithin said cavity supported on a second axle for pivotal movementbetween two switching positions, said second axle having an axis alignedparallel to said axis of said first axle, said second axle mounted on, apin supported by said second wall, said armature comprising two separateblocks of magnetic material, a non-magnetic supporting'means for saidblocks, a first ,contact support means in contact with said second axle,and first contact means mounted on said first contact support means; anda second contact means mounted within said cavity on a second contactsupport means, said second contact support means supported by saidsecond wall, whereby one actuating portion of each of said pole pieces,said magnet, two of said inserts, and one of said blocks form a strongmagnetic circuit to maintain contact between said first and secondcontact means whenever saidactuator is positioned in one of saidswitching positions.

7. The combination set forth inclaim 6, wherein said blocks have thecharacteristics of high resistivity, high Curie point, high permeabilityat low flux density, and low coercive force.

8. The combination set forth in claim 7, wherein said strong magneticcircuit comprises a small air gap between said two insets and said blockfor every position of said armature.

9. The combination set forth in claim 6, wherein said blocks are mildsteel.

10. The combination set forth in claim 6, wherein said strong magneticcircuit comprises a small air gap between said two inserts and saidblock for every position of said armature.

11. In an electrical switch, the combination comprising: a supportinghousing, said housing comprising a hermetically sealed switching cavityand first and second rigid walls, said first wall comprising a bodyportion of nonmagnetic material with four apertures therein arranged ina generally rectangular configuration and an insert of magnetic materialhermetically sealed within each of said apertures; a magnetic actuatorsupported on a first axle mounted on said housing externally of saidcavity on one side of said first wall for pivotal movement between twoswitching position, said first axle having an axis, said actuatorcomprising a permanent magnet having N and S poles and a magnetic axisaligned parallel to said axis of said first axle, said magnetic having apole piece integrally mounted on each of said N and S poles, each ofsaid pole pieces having a pair of depending actuating portions, saidactuating portions aligned so that,one actuating portion of each of saidpole pieces is in substantial contact with said one side of said firstwall whenever said actuator is in one of said switching positions, eachof said actuating portions aligned with one of said inserts; an armaturewithin said cavity supported on an electrically conductive bearing forpivotal movement between two switching positions, said bearing having anaxis aligned parallel to said axis of said first axle, said bearingmounted on an electrically conductive pin supported by said second wall,said armature comprising two separate blocks of magnetic material, anon-magnetic supporting means for said blocks, an electricallyconductive bushing concentric with said bearing, a first contact supportmeans in electrical contact with said bushing, and first contact meansmounted on said first contact support means; and secondcontact meansmounted within said cavity on a second contact support means, saidsecond contact support means supported by said second wall, whereby oneactuating portion of each of said pole pieces, said magnet, two of saidinserts, and

one of said blocks form a strong magnetic circuit to maintain contactbetween said first and second contact means whenever said actuator ispivoted into one of said switching positions, and the pivotal motion ofsaid bushing on said bearing provides a substantial wiping actiontherebetween.

12. The combination set forth in claim 11 wherein said blocks have thecharacteristics of 'high resistivity, high Curie point, highpermeability at low flux density and low coercive force. V

13. The combination set forth in claim 12, wherein said strong magneticcircuit comprises a small air gap between said two inserts and saidblock for every position of said armature.

14. The combination set forth in claim 11, wherein said blocks are mildsteel.

15. The combination set forth in claim 11, wherein said strong magneticcircuit comprises a small air gap between said two inserts and saidblock for every position of said armature.

References Cited in the file of this patent UNITED STATES PATENTS FranceJan. 24,

1. IN AN ELECTRICAL SWITCH, THE COMBINATION COMPRISING: A SUPPORTINGHOUSING, SAID HOUSING COMPRISING A SEALED SWITCH CAVITY AND A RIGIDWALL, SAID WALL COMPRISING A BODY PORTION OF NON-MAGNETIC MATERIAL WITHFOUR APERTURES THEREIN ARRANGED IN A GENERALLY QUANDRANGULARCONFIGURATION AND AN INSERT OF MAGNETIC MATERIAL SEALED WITHIN EACH OFSAID APERTURES; A MAGNETIC ACTUATOR MOUNTED ON SAID HOUSING EXTERNALLYOF SAID CAVITY FOR MOVEMENT BETWEEN TWO SWITCHING POSITIONS, SAIDACTUATOR COMPRISING A PERMANENT MAGNET HAVING N AND S POLES, EACH OFSAID POLES HAVING A PAIR OF ACTUATING PORTIONS SAID ACTUATING PORTIONSALIGNED SO THAT ONE ACTUATING PORTION OF EACH OF SAID POLES IS INSUBSTANTIAL CONTACT WITH SAID WALL WHENEVER SAID ACTUATOR IS IN ONE OFSAID SWITCHING POSITIONS, EACH OF SAID ACTUATING PORTIONS ALIGNED WITHINE OF SAID INSERTS; AN AMATURE WITHIN SAID CAVITY SUPPORTED BY SAIDHOUSING FOR PIVOTAL MOVEMENT BETWEEN TWO SWITCHING POSITIONS, SAIDARMATURE MAGNETICALLY ASSOCIATED WITH SAID ACTUATOR SO THAT SAIDARMATURE ASSUMES A PREDETERMINED ANGULAR POSITION FOR EACH OF SAID TWOSWITCH POSITIONS, SAID ARMATURE COMPRISING TWO SEPARATE BLOCKS OFMAGNETIC MATERIAL, A NON-MAGNETIC SUPPORTING MEANS FOR SAID BLOCKS, ANDFIRST CONTACT MEANS MOUNTED THEREON; AND SECOND CONTACT MEANS WITHINSAID CAVITYY SUPPORTED BY SAID HOUSING, WHEREBY ONE ACTUATING PORTION OFEACH OF SAID POLES OF SAID MAGNET, TWO OF SAID INSERTS, AND ONE OF SAIDBLOCKS FROM A STRONG MAGNETIC CIRCUIT TO MAINTAIN OF SAID BETWEEN SAIDFIRST AND SECOND CONTACT MEANS WHENEVER SAID ACTUATOR IS POSITIONED INONE OF SAID SWITCHING POSITIONS.